Hydraulic brake boosters, such as disclosed in U.S. Pat. No. 3,831,491, have been proposed for general use in vehicles because of their compactness and reliability. In such brake boosters, the input force from the operator, which is modified through a ratio changer, moves a valve to allow a proportional volume of fluid under pressure to actuate the wheel brakes of the vehicle.
In order to maintain the number of components attached to the drive train of the motor of the vehicle at a minimum, it was suggested, as disclosed in U.S. Pat. No. 3,838,629, that a portion of the output of the pump that supplies the power steering gear be diverted to operate the hydraulic brake booster.
In a further effort to better utilize the space available under the hood of vehicles, my U.S. patent application 670,513, now U.S. Pat. No. 4,072,011, discloses a single structure for retaining both a hydraulic brake booster and a power steering gear. A flow control valve in the housing in response to a brake actuation signal diverts a portion of the output of the pump away from the rotary valve in the steering gear to provide the hydraulic brake booster with a power assist.